Assessing Outlook 2000?s impact on Terminal Services

You know that Terminal Services allows you to run application software hosted on your Windows server. But what kind of an impact does an application like Outlook have on your server? Brien Posey takes a look.

If you’ve recently upgraded to Exchange 2000 or have been looking to doing so, you might have discovered that your clients can’t take advantage of every feature unless they’re running Outlook 2000 or are using the Outlook Web Access. However, in some environments, it may not be possible to configure each client to use Outlook 2000. If the machines have insufficient hardware or if you don’t have enough money in the budget to buy copies of Outlook 2000, you may be stuck with your existing mail client software.

Fortunately a Windows 2000 component called Terminal Services can take care of this problem for you. In this Daily Feature, I’ll show you what impact running Outlook 2000 will have on a server running Terminal Services.What is Terminal Services?
The easiest way to explain Terminal Services is to compare it to a mainframe environment. In a mainframe environment, the mainframe performs every bit of the processing. The clients attach to the mainframe through dumb terminals, which have absolutely no processing power of their own. The mainframe sends screens full of information to the dumb terminals. Whenever the end user enters data, the data is sent back to the mainframe for processing. The mainframe processes the request and sends back an updated screen.
In a Terminal Services environment, the Windows 2000 server that’s running Terminal Services does most of the work. Instead of using dumb clients, though, the end users use standard PCs or any other device that’s capable of running Terminal Server client. The Windows 2000 server sends screens of information to the clients and then waits for user input. When the user enters data, the data is sent to Terminal Server for processing. Terminal Server processes the data and then sends the user an updated screen. For more information about Terminal Services, see the Daily Drill Down “Introducing Windows 2000's Terminal Services.”Terminal Services and Outlook 2000Because of the way Terminal Services works, clients that would normally be incapable of running software such as Outlook 2000 can now do so because they don’t actually have to run the software themselves. Instead, they just have to run a Terminal Server client, which is a very small application that just about any Windows-based PC can run. In fact, there’s even a version of the Terminal Server client that runs on Windows CE machines.

To make Outlook work with Terminal Services, you only need to load a single copy of the Outlook 2000 software on the server. The first time each client accesses Outlook 2000, you may have to configure client-specific settings, such as the name of the user’s mailbox. Once you’ve done that, Outlook should run through Terminal Services with no problems.

As far as the load that Outlook places on the server though, you may be surprised to learn that Outlook 2000 places about the same load on Terminal Server as Outlook 97 does. Remember that Terminal Server clients only transmit keystrokes and mouse movements to the server. Therefore, if a user has Outlook 2000 open but is merely waiting for an e-mail, they aren’t placing much of a load on Terminal Server. There is some load placed on Terminal Server because some memory and a minimal amount of processing power are required to keep the idle session running. However, when a Windows 2000 session is sitting idle, no screen updates are being passed back and forth, so very little network bandwidth is being used by the session.

What about those times when an Outlook session isn’t idle? The act of reading an e-mail message doesn’t place much strain on the server. The user simply double-clicks on a message and Outlook displays it. This act requires minimal processing power and only involves a single screen update. The exception to this would be a really long message that the user has to scroll through to read. The act of scrolling through a message requires many screen updates to be performed in rapid sequence. Therefore, a considerable amount of network bandwidth is consumed, and the server must use some processing power to generate these screen updates.

Also, some e-mail messages include attachments. In a Terminal Server environment (like any other environment), the attachment is simply displayed as an icon until the user double-clicks on it to open it. Therefore, until the user opens the attachment, the message doesn’t require any more power from Terminal Server than any other message does. When the user does open the attachment, the amount of power that’s required will depend on the type of attachment.

What about the act of composing a message? As I mentioned, the only things that get transmitted by the client are keystrokes and mouse movements, and the only thing that gets transmitted by the server back to the client is screen updates. Therefore, composing an e-mail message is a fairly intense process. Every keystroke that the user makes while typing his/her message must be sent to Terminal Server. Terminal Server must then plug the keystroke into the Outlook 2000 software and then transmit a screen update back to the client. This process requires a significant amount of processing to be done on the server and eats up some bandwidth. The amount of power and bandwidth required, however, is less than the amount that a client consumes when the user moves the mouse.

When a user moves the mouse, the client machine must quickly transmit the pointer’s coordinates to the server. The server must render a screen that displays the mouse’s position and transmit the screen back to the client. Because this process must happen several times per second, it is one of the most strenuous tasks for a Terminal Server. About the only thing that you can do on a Terminal Server client that would place more of a load on the server and consume more network bandwidth would be to use an application that involves a lot of mouse movement and a lot of animation. An example of such an application would be a video game.

ConclusionAll in all, Outlook 2000 doesn’t place nearly as much of a load on a Terminal Server as some other applications do. Using a Terminal Server to support your Outlook 2000 clients can tremendously ease your administrative burden. Just make sure that your server has plenty of available hardware resources, or your clients could be in for a very slow computing experience.